This invention relates to a silver halide light-sensitive element, and more particularly to a silver halide photographic light-sensitive element which is capable of providing a very stable latent image (in other words, a reduction in latent image regression).
As is known in the art, the formation of an image according to a silver halide photographic method requires a projection light-exposure process to form a latent image and a development processing process to convert the latent image thus-formed into the corresponding silver or dye image (see, for example, Mees & James, The Theory of the Photographic Process, 4th Ed., 1977).
The formation of a latent image according to the projection light-exposure process results from extremely small changes in silver halide crystals when considered from a chemical standpoint, and the latent image itself is somewhat unstable. Over a period from the time of the projection light-exposure process to the time of the development processing process, the intensity of the latent image is liable to decrease. This phenomenon is generally called "latent image fading". The rapidity of the latent image fading varies generally depending on the conditions under which an exposed light-sensitive element is stored; for example, when the exposed light-sensitive element is stored at a high temperature, the latent image fading is generally significant, whereas when stored at a low temperature, it is generally less significant.
One simplified method for overcoming disadvantages resulting from the latent image fading is to carry out the development processing immediately after the projection light-exposure, and a second simplified method is to store the exposed light-sensitive element at a low temperature. Although these methods are the easiest from a chemical standpoint, they are often not convenient for the user. Negative elements and reversal elements are often allowed to stand at room temperature for several months after light-exposure before they are subjected to the development processing. Even with positive elements for duplication, it is sometimes allowed to stand for several months.
It is therefore desirable to prepare a light-sensitive element which is capable of providing a stable latent image by application of a specific procedure in the course of the production thereof. In order to obtain such light-sensitive elements, various methods have heretofore been proposed, including a light-sensitive element as disclosed in West German Pat. No. 1,170,508 in which a hydroxy group-substituted aromatic compound is used, a light-sensitive element as disclosed in U.S. Pat. No. 3,447,926 in which 1,3-diones are used, a light-sensitive element as disclosed in U.S. Pat. No. 3,318,702 in which nitrilotriacetic acid, etc., are used, a method as disclosed in West German Pat. No. 1,173,339, and a method as disclosed in U.S. Pat. No. 3,424,583.
Further, the use of penicillin derivatives in photographic emulsions has been proposed to reduce latent image regression (British Pat. No. 1,389,089).
It has been found, however, that these known methods fail to provide light-sensitive elements which are completely satisfactory with respect to the latent image fading, and further improved stability would be desirable.